The result puts her within 30 delegates of the 2,383 needed to claim the nomination, according to an Associated Press tally.
Residents of Puerto Rico, a US territory, can vote in presidential primaries but cannot take part in the November general election.
Both Ms Clinton and her progressive rival, Vermont Senator Bernie Sanders, have been campaigning hard in California, where polls put them in a dead heat ahead of Tuesday’s primary.
Five other states are also holding Democratic primaries on Tuesday, the last major day of primary season – New Jersey, Montana, New Mexico and the Dakotas – with a total of 694 delegates in play.
Ms Clinton, who has won almost three million more votes than Mr Sanders, is expected to reach the 2,383 threshold when the polls close in New Jersey at 8pm Eastern Time on Tuesday.
However, Mr Sanders has pointed out that her delegate total relies on those super-delegates who have offered Ms Clinton their support, but who do not actually cast their votes until the Democratic convention in Philadelphia in July.
Victor Manuel / macho20022(at)BELTRAN Priscilla / beltran-p6(at)CUSIMANO SANTOS Carmen A.
/ ada1842(at)DELGADO Janet / Janet(at)DEMICHELLI Fiorella / fdemichelli(at)ESTEVEZ Robert / cuteprboy21peace(at)FIGUEROA Edgardo / angeloedgar(at)GONZALEZ Alberto / lafamilia4(at)GONZALEZ-MARTINEZ Milagros / tuamigadelsilencio(at)HERENCIA De Los SANTOS Luis Roy / LUISROY2002(at)HOTMAIL.
COM HERNANDEZ Jorge / titoccd(at)IGARTUA Xabier / xabierigartua20(at)JIMENEZ LEON Julio Cesar / julio_cesarj(at)LOPEZ Ricardo / Ric_Lop(at)LOZADA Wanda / wandailozada(at)MARTINEZ Olga / olga13_66(at)MERCADO Vivinna / viviannaannette(at)MORALES Betty / bettyblond30(at)NEGRONI DE ALICEA Maggie W. COM NU�EZ del PARADO REYES Yenifer / yenunez(at)PAGAN-CRUZ Shemaiah Lin / SUNSHINELIN1973(at)YAHOO.COM RAMIREZ Jorge / jorqui53(at)RAMOS RIVERA Lourdes / LULUJOEL5PR(at)AOL.COM RIVERA Sheila / Strawberrie_pr96(at)RODRIGUEZ Hector M./ manrodcollazo60(at)RODRIGUEZ Naschabell / Qeentazldy01(at)RODRIGUEZ Yolanda / yolanda Yau(at)RODRIGUEZ CASTRO Jhonny Tito / jhonnyrodriguez(at)ROMERO Glorivette / CGCJ(at)ROMERO Grace V./ gvromero(at)ROSARIO Caroline / lawtay30(at)RUIZ DEL VALLE Maria / Farmouse72(at)SALAS RIVERA Peter / Peter Salas USA68(at)TORRES Rivera Mar�a E.Hillary Clinton edged ever nearer to the Democratic presidential nomination on Sunday night, winning the party’s primary in Puerto Rico with a projected 60 per cent or more of the vote.